Telescopic sights have a lead mark, for example in the form of a reticle. In order to be able to adjust the lead mark to the actual point of impact for specific ballistics (caliber, projectile mass, type of projectile, charge, etc.) and a specific barrel for a specific zero range, the lead mark is usually adjustable for elevation and deflection in known manner by means of an adjusting mechanism.
In addition, different construction designs have been disclosed that make it possible to index the adjusted position by means of an index mark (zeroing).
With such designs, however, it is usually only possible to index one specific setting, ie only one zero mark, for the point of impact for specific ballistics using a specific barrel for just one shooting range.
An actuator of the type described at the outset for use on a telescopic sight and enabling multiple zeroing, ie zeroing for a number of ranges and/or for different ballistics and/or different gun barrels etc., is disclosed, for example, by Leatherwood (USA) under the name of “Uni-Dial” (see also US 2004/0144013 A1). This actuator exhibits a number of indicator flags that can be rotated in the actuator. The actuator is embodied in the form of a rotary knob that consists of several disk-shaped elements positioned around the axis of rotation of the unit. The flags are disposed on flat disks located between the disk-shaped elements of the rotary knob (turret) (in the disclosed embodiment the disk-shaped elements of the rotary knob are substantially thicker than the disks having the flags) and are displaceable in an adjustment mode of the actuator, ie the disks on which the flags are located can be rotated about the axis of rotation without the lead mark itself being displaced.
In the operating mode, after zeroing for different ranges, barrels, etc., the flags are fixed in their adjusted position by screwing, or otherwise fixing, the rotary knob, that is to say, the plates that form the rotary knob, such that the said plates are pressed tightly against each other so that the flag indicator plates are squeezed between the disks of the rotary knob and are entrained with the knob when the latter is rotated.
Irrespective of whether only “single” indexing or “multiple” indexing is possible when using an actuator of the aforementioned type, an actuator has a given adjustment range for control of the lead mark. This adjustment range is limited by at least one operating range limit stop. Either two separate operating range limit stops are provided that restrict the rotary motion of the rotary knob, or only one operating range limit stop serves as both the upper and lower stop, while, depending on the dimensions of the operating range limit stop device, a turn of almost 360° is possible, typically approx. 330°. The limitation of the overall range of possible adjustment to one adjustment range serves to avoid indexing ambiguities.
Actuators have also been disclosed in which the adjustment range is not restricted by means of operating range limit stops. To enable a user to know at what position the rotary knob is set, ie how many turns the rotary knob has made starting from an initial setting, horizontal bars are provided which are either hidden or made visible as the rotary knob is turned.
Such a system makes an additional adjustment range of the lead mark possible. Such a system is of particular interest to the military. Since in such systems the individual index marks are defined by vertical bars and thus a large number of adjustments is possible, the user of such a rifle needs, for use, lists in which the individual index marks are defined, particularly in connection with the number of full turns of the rotary knob.
Such a high degree of accuracy is not necessary in hunting, and the shooting ranges encountered in hunting are restricted to a significantly narrower range than that required by the military.
On the other hand, in hunting it is necessary that the lead mark of a sight of a rifle can be indexed simply and quickly and without the use of said lists, eg for four different ranges, and that such ranges can be quickly and simply set by the user. For this reason, in hunting, actuators for telescopic sights are mainly used that have an operating range limit stop as is the case on the aforementioned telescopic sight sold by Leatherwood.
With this telescopic sight, the operating range limit stop is defined by a screw that can be loosened. By loosening and turning the screw along the periphery of the actuator, the stopping point and thus the adjustment range of the lead mark can be adjusted in relation to the entire possible adjustment range.
This solution, however, has some drawbacks in practice. The procedure of loosening, turning, and subsequently tightening the screw is relatively complicated. There is a risk of losing the screw. In addition, the system can become contaminated with dirt relatively easily, which might lead to deterioration of the adjustability.